Double-chamber piston pump for the distribution of fluid products

ABSTRACT

A piston pump is disclosed suitable to be installed on machines for dispensing fluid products, comprising a jacket, a piston device mobile with alternate motion inside said jacket and comprising a rod and a head. The pump also comprises a pipe for fluids to enter and a pipe for fluids to exit, said pipes being disposed on the same side of the jacket and on opposite sides with respect to the piston device.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention concerns a piston pump for the distribution offluid products such as, for example, colorant liquids, paint bases,varnishes, enamels, inks and suchlike, located inside containersinstalled on dispensing or distribution machines of fluid products. Inparticular, the invention concerns a piston pump characterized byparticular geometric solutions that allow to obtain an improvement inthe delivery performances of the fluid product at least in terms ofprecision and repeatability.

Description of Related Art

Machines are known for dispensing or distributing fluid products, suchas for example colorants with different tones or hues, able to be mixedwith each other and/or added to a base substance in order to create avarnish or paint of a determinate color.

Known machines normally comprise a plurality of containers containing adeterminate colorant, able to be selectively connected to one or moredelivery nozzles and connected to respective pump means that cause theselective delivery of the fluid product in a suitably chosen quantity,with the help of an electronic processor for example.

It is known that to obtain accuracy and repeatability of the doses ofdyes to be mixed it is fundamental to make a suitable choice of the pumpmean.

It is known that, among pump means used to deliver fluid products,volumetric pumps of the piston type are used, with a single chamber, ora double chamber.

It is also known that single-chamber volumetric piston pumps arecharacterized by a single work chamber with a well-defined volume. Thevolume is determined by the travel effected by the piston and by thediameter of the chamber itself, and the sizes are defined on the basisof the requisites that a dispensing machine must satisfy. For example,the requisites can include delivery time, delivery flow, deliveryquantity, not to mention the bulk.

Moreover, a single-chamber volumetric piston pump, because of how it isconfigured, is simple to make, compared to a double-chamber piston pump,and also entails a simplicity of the hydraulic circuit connected to it.

One disadvantage of the application of a single-chamber piston pump isthe long delivery times of the fluid product. Indeed a single-chambervolumetric piston pump provides a suction step of the fluid product fromthe container inside the chamber itself. This step represents a waitingtime, that is, a non-delivery time, which lasts from the activation stepof the pump until the complete filling of the chamber, that is, when thepiston reaches its end-of-travel. The delivery begins in thedistribution step, that is, when the piston inverts its travel anddelivers the fluid product from the pump chamber to the final container(for example, a can, a bottle, or a jerry can).

It is also known that the piston pumps with two chambers at least partlysolve the disadvantage of long delivery times. In fact, alternating thechambers involved by the suction and delivery steps allows a substantialoperative continuity without downtimes. Therefore, with a double-chamberpiston pump there is an appreciable optimization of the delivery timesof the fluid product.

The U.S. Pat. No. 8,191,733 B2 describes a double-chamber piston pump,in which the small plate of the piston comprises a non-return valvedisposed advantageously in the direction of the delivery flow. Thenon-return valve thus disposed allows a simultaneous suction anddistribution process, as well as determining a substantially lineartravel of the hydraulic circuit. Moreover, the two chambers of thepiston pump have different sizes from each other since the secondchamber, comprised between the piston and the second end-of-travel, hasa smaller volume than the first by a volume equal to the volume occupiedby the piston rod. This difference in volume, in cooperation with thenon-return valve comprised inside the piston, allows the fluid productto flow in the delivery direction.

The concept of a different volume between two chambers of a piston pumpis also applied in patent US 2011/0259918 A1, but in differentembodiments. In particular, a non-return valve comprised in the pistonis not provided. This absence is compensated by a different hydrauliccircuit that provides two non-return valves during suction and thereforetwo distinct entrances in the piston pump, one for each of the twochambers. During delivery, two non-return valves are always providedcorresponding to two different exits from the piston pump, one for eachof the two chambers. The principle that governs the flow of the fluidproduct from a suction pipe to a delivery pipe is based on the alternatemovement of the piston inside the central pumping pipe.

The solution of US 2011/0259918 provides the entrance of the fluid in aposition opposite the exit. Therefore, this solution cannot be used inall the cases in which, for structural reasons for example, the entrancemust be positioned on the same side as the exit, that is, so that theentrance and exit pipes are parallel to each other and with the entranceand exit facing in the same direction.

Moreover, the solution of US 2011/0259918 provides long travels of thepistons and an asymmetrical disposition and behavior thereof.

Document U.S. Pat. No. 5,156,537 (US'537) describes a pumping device toseparate, inside the same device, the liquid and gas components of thefluid to be delivered.

In this case, the shaft on which the head of the piston of the pump ismoved is present in only one of the two chambers and this determines adifference in volume of the two delivery chambers. This difference involume determines poor accuracy in the dosage of the fluid products,which is not however required in US'537 given the large quantities offluid moved at each pumping cycle, and poor repeatability in the dosageof the fluid. Moreover, this difference in volume also determines adifferent duration of the suction and delivery steps of the fluidproduct into and from the two chambers. This causes an asymmetry in thedelivery and suction times from which ensue time intervals in which thefluid product is not delivered.

Document U.S. Pat. No. 4,008,012 describes a pumping device for foodproducts with two chambers, where the upper chamber, having part of itsvolume occupied by the end-of-travel mechanisms, has a smaller volumethan the lower chamber.

Documents U.S. Pat. Nos. 2,368,013, 1,498,471 and GB 1522552 describeother pumping devices which have the same problems as those described inthe cited known documents, that is, a difference in volume between thetwo chambers and a consequent asymmetry in the delivery and suctiontimes.

BRIEF SUMMARY OF THE INVENTION

One purpose of the present invention is to make a piston pump thatallows high levels of accuracy and repeatability of the doses.

It is also a purpose of the present invention to make a double-chamberpiston pump that allows to keep the durations of the suction anddelivery steps of the fluid equal in the two chambers without timeintervals during which the fluid is not delivered.

Another purpose of the present invention is to make a double-chamberpiston pump that allows to simplify the control of the doses to becarried out.

Another purpose of the present invention is to make a double-chamberpiston pump that provides rapid delivery times, even for largequantities of fluid product, but without increasing the sizes of thepiston pump and therefore increasing its bulk.

The Applicant has devised, tested and embodied the present invention toovercome the shortcomings of the state of the art and to obtain theseand other purposes and advantages.

The present invention is set forth and characterized in the independentclaim, while the dependent claims describe other characteristics of theinvention or variants to the main inventive idea.

In accordance with the above purposes, a double-chamber piston pumpaccording to the present invention, suitable to be installed in stationsfor the delivery of fluid products, comprises a hollow body divided intotwo chambers by a piston device so that said two chambers have the samevolume.

According to a first characteristic of the present invention, the twochambers are respectively defined by the position of the head of thepiston device, on the respective opposite sides thereof, and arealternatively operating in suction and in delivery thanks to thealternate drive of respective suction and delivery valves, disposedsymmetrically at the sides of the shaft of the piston device.

In a preferred formulation of the invention, the shaft of the pistondevice defines the longitudinal median axis of the piston pump.

According to the present invention, the installation diagram of thevalves with respect to the body of the piston pump can be described asan anti-parallel disposition.

In a preferred formulation, the piston device is actuated by ahigh-resolution step motor.

The piston device comprises, as we said, a head and a rod. In anadvantageous embodiment, the head is made of a plastic or metalmaterial, resistant to friction forces and to the temperatures that aregenerated during the delivery activity.

The double-chamber piston pump, according to the present invention, isconfigured with sizes studied specifically to be able to carry outdeliveries of big and small quantities of fluid product, at the sametime maintaining high levels of accuracy and repeatability of the doses.Therefore, the hollow body will have sizes suitable to convey anadequate flow of fluid product. In particular, the sizing of the bore ofthe hollow body is dependent on the performances of the pump and isdecisive for the definition of the diameter of the rod.

In accordance with another characteristic of the present invention, thevalves are of the one-way or non-return type. The valves are comprisedin an entrance and exit device, each in correspondence to an entrance orexit aperture, and are installed so as to assist the direction of flowof the fluid product.

According to one characteristic of the present invention, theintroduction pipe of the fluid material inside the chambers of the pumpand the delivery pipe of the fluid material are on the same side of thepump.

According to another characteristic, said pipes develop substantiallyparallel to each other and substantially parallel to the rod of thepiston.

According to another characteristic, the suction and delivery valvesconnected with a first chamber of the piston are disposed, one withrespect to the other, on opposite sides with respect to the median axisof the body of the pump, while the suction and delivery valves connectedwith the other, second chamber of the piston are symmetrical andspecular with respect to the valves of the first chamber.

During functioning, the suction valve associated with the first chamberand the delivery valve associated with the second chamber are open atthe same time during a first travel of the piston in a first direction,while the delivery valve associated with the first chamber and thesuction valve associated with the second chamber are open at the sametime during a second travel of the piston in a second direction,opposite the first direction.

The double-chamber piston pump allows the suction and distribution stepsof the fluid product to be performed simultaneously. Indeed, while onechamber is affected by a positive distribution flow, the other chamberhas an equal and negative suction flow.

Another purpose of the present invention is to define a dispensingprocess of the fluid products that allows the suction and distributioncondition to be carried out simultaneously in the two chambers of thepiston pump. In particular, one step consists in sliding the pistondevice from a lower end of the hollow body to an upper end of the hollowbody; the other step, on the other hand, consists in sliding the pistondevice from the upper end to the lower one. In their turn, the valveswill be opened and closed according to the logic of anti-paralleldistribution. When a chamber is in the suction condition, the entrancevalve is open to allow the entrance of the fluid product into thechamber and to prevent its exit with the exit valve closed. On thecontrary, when the chamber is in a distribution condition the exit valvewill be open to facilitate the exit of the fluid product from thechamber and the entrance valve will be closed to prevent the flow fromflowing backward.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other characteristics of the present invention will becomeapparent from the following description of some embodiments, given as anon-restrictive example with reference to the attached drawings wherein:

FIG. 1 is a section view of the piston pump during a functioning step;

FIG. 2 is a section view of the piston pump during a functioning step;

FIG. 3 is a graph of the progress of the flow; and

FIG. 4 is is a view of the piston pump with the motor.

DETAILED DESCRIPTION OF THE INVENTION

To facilitate comprehension, the same reference numbers have been used,where possible, to identify identical common elements in the drawings.It is understood that elements and characteristics of one embodiment canconveniently be incorporated into other embodiments without furtherclarifications.

We shall now refer in detail to the various embodiments of the presentinvention, of which one or more examples are shown in the attacheddrawing. Each example is supplied by way of illustration of theinvention and shall not be understood as a limitation thereof. Forexample, the characteristics shown or described insomuch as they arepart of one embodiment can be adopted on, or in association with, otherembodiments to produce another embodiment. It is understood that thepresent invention shall include all such modifications and variants.

In accordance with the embodiments of FIGS. 1, 2 and 4, the inventionconcerns a double-chamber piston pump 10, hereafter simply called pistonpump, installed on machines for dispensing fluid products.

Hereafter in the description, merely by way of non-restrictive example,the fluid product is indicated as a dye, but it can be any othercolorant liquid, such as for example a paint base, enamel, an ink orsuchlike.

The piston pump 10 comprises an entrance device 11 able to connect thepiston pump 10 to the container (not shown in the drawings) thatcontains the dye.

The entrance device 11 comprises an entrance pipe 12 that connects thecontainer of the dye to the piston pump 10. The entrance pipe 12 candivide into two distinct entrances, an upper 13 and a lower 14, whichallow the dye to enter respectively into an upper 15 and a lower 16chamber during the suction step in each chamber.

The chambers 15 and 16 are here defined upper and lower with referenceto the drawing, though this definition is intended merely for ease ofillustration.

Each entrance can comprise a one-way or non-return valve 17, installedso as to promote the flow of the dye in the distribution direction,avoiding possible flows in the opposite direction.

The valves are defined here as 17 a, 17 b, 17 c, 17 d. In particular, aswill be described in more detail hereafter, the valves 17 a and 17 d arerespectively the suction and delivery valves connected to the firstupper chamber 15, while the valves 17 b and 17 c are respectively thesuction and delivery valves connected to the second lower chamber 16. Ascan be seen in the drawings, the valves 17 a, 17 d, connected to thefirst upper chamber 15, are disposed on opposite sides with respect tothe median axis of the pump and specular and symmetrical with respect tothe corresponding valves 17 b, 17 c connected to the second lowerchamber 16.

The internal mechanism of the piston pump 10 comprises a jacket 18,configured as a hollow body.

The jacket 18 comprises an upper end-of-travel 27 and a lowerend-of-travel 28.

In a particular embodiment, the jacket 18 is configured so as to have abore that goes from 35 mm to 45 mm, preferably 40 mm, or from 50 mm to60 mm, preferably 54 mm.

The piston pump 10 comprises a piston device 19 that slides inside thejacket 18 and allows to achieve the alternate steps of suction anddistribution of the dye.

The jacket 18 can be made of stainless steel, or of technical ceramic,or any other metal or material resistant to the forces and otherstresses that are generated inside during functioning.

The piston device 19 comprises a head 20 with sizes complimentary to thebore of the jacket 18 and such as to allow the piston device 19 to slideinside it.

The head 20 can be made of a plastic material resistant to the forcesand temperatures that originate from mechanical sliding, for examplePTFE (polytetrafluoroethylene), or other suitable material.

The head 20 of the piston device 19 defines, respectively above andbelow it, the two chambers 15 and 16 of the piston pump 10 that containthe same volume of the fluid product.

This structure allows to alternately deliver always the same quantity offluid, independently from the chamber 15 or 16, inside which the fluidproduct is taken in.

The piston device 19 also comprises a rod 21 firmly connected at one endto the head 20, while the remaining end is connected to ahigh-resolution step motor 29.

The rod 21 can be made of a material resistant to the stresses occurringduring the drive of the motor 29, for example stainless steel or analuminum alloy.

In a particular embodiment, the rod 21 can be configured so that theratio between its cross section and the section of the bore of thejacket 18 is no higher than 0.25.

The piston device 19, during functioning, slides inside the jacket 18from the upper end-of-travel 27 to the lower end-of travel 28 and viceversa. The volumes of the upper 15 and lower 16 chambers are equal toeach other and depend on the bore of the jacket 18, and also vary duringthe travel of the piston device 19.

In a particular embodiment, the travel of the piston device 19 has alength from about 10 mm to about 15 mm, preferably 12 mm. Therefore themaximum volume of both the chambers 15 and 16 is given by the volume ofthe jacket 18 minus the bulk volume of the same portion of the head 20and the rod 21.

The piston pump 10 comprises an exit device 22 able to allow the exit ofthe dye from the jacket 18 and thus to direct the dye toward the finaldistribution elements (not shown in the drawings) of the dispensingmachine.

The exit device 22 can comprise an exit pipe 23 comprising two exits,respectively an upper exit 24 and a lower exit 25, each of which cancomprise a one-way or non-return valve 17, respectively 17 d and 17 c,disposed so as to assist the flow of dye exiting from the two chambers15 and 16.

It should be noted that the axial-symmetrical and specular position ofthe valves 17 a, 17 b, 17 c and 17 d defines the positions of the exits24 and 25 at the same height as the entrances 13 and 14, rendering theflows of the two chambers 15 and 16 coherent and homogenous with respectto each other.

Moreover, the entrance pipe 12 and the exit pipe 23 are advantageouslydisposed on the same side of the piston pump 10, they are parallel toeach other and end substantially at the same height, thus promoting theassembly of the piston pump 10 into a dispensing machine for fluidproducts.

The piston pump 10 can comprise a support 26 that can be attached to asurface of the dispensing machine for fluid products.

This support 26 allows to be able to use the piston pump 10 in anyorientation, keeping the orientation of the entrance pipe 12 and theexit pipe 23 always in a common direction.

Always with reference to FIGS. 1 and 2, the functioning of the pistonpump 10 can be schematically synthesized in two principal stepsdistinguished by the direction of movement of the piston device 19.

A first step consists in sliding the piston device 19 from the lowerend-of-travel 28 to the upper end-of-travel 27 of the jacket 18, thatis, upward as shown in FIG. 1. The first upper chamber 15 is in deliverymode with the valve 17 a of the upper entrance 13 closed and the valve17 d of the upper exit 24 open. At the same time, the second lowerchamber 16 is in suction mode with the valve 17 b of the lower entrance14 open and the valve 17 c of the lower exit 25 closed.

Once the piston device 19 has reached the upper end-of-travel 27, itinverts the sliding direction in the direction of the lowerend-of-travel 28, that is, it moves downward as shown in FIG. 2. Thefirst upper chamber 18 is in suction mode with the valve 17 a of theupper entrance 13 open and the valve 17 d of the upper exit 24 closed.At the same time, the second lower chamber 16 is in delivery mode withthe valve 17 b of the lower entrance 14 closed and the valve 17 c of thelower exit 25 open.

Functioning this way is allowed with the configuration of the valves 17in anti-parallel.

The functioning of the piston pump 10 can be summarized as simultaneoussuction and distribution steps that last the same length of time andthrough which the same quantity of dye flows.

The simultaneous nature of the suction and delivery steps of the dye isgiven by the presence of two chambers inside the jacket 18.

Moreover, according to an embodiment previously described and withreference to FIG. 3, the volume of the two chambers 15 and 16 allows tohave, inside the jacket 18, in normal working conditions, one chamberthrough which a flow with a positive sign passes (distribution step) andthe other chamber through which an equal flow and with the opposite signpasses (suction step). Therefore, the fact that the upper 15 and lower16 chambers have the same volume allows to improve the accuracy andrepeatability of the doses, provided that this aspect is combined withthe high-resolution actuation exerted by the step motor 29 controlled inposition and in current by suitable sensors. This embodiment allows toachieve a simplified control of the doses by the electronic processor,in particular for very low quantities delivered (most criticalcondition).

According to the illustration in FIG. 3, providing two chambers withequal volume means obtaining equal suction and delivery times and thisalso means having an inversion of the steps in the two chambers 15, 16at the same moment, guaranteeing the continuity of the delivery process.

The embodiments described above allow to make a double-chamber pistonpump 10 able to deliver a quantity of dye in a short time thanks to thedouble-chamber system and to the geometric characteristics of themechanical system that allows a flow of dye delivered that goes from0.371 l/min to 1.639 l/min, preferably 0.582 l/min, or 1.094 l/min.

It is clear that modifications and/or additions of parts may be made tothe double-chamber piston pump for fluid products as describedheretofore, without departing from the field and scope of the presentinvention.

It is also clear that, although the present invention has been describedwith reference to some specific examples, a person of skill in the artshall certainly be able to achieve many other equivalent forms ofdouble-chamber piston pump for fluid products, having thecharacteristics as set forth in the claims and hence all coming withinthe field of protection defined thereby.

I claim:
 1. A piston pump suitable to be installed on a machine fordispensing fluid products, comprising a jacket, a piston device mobilewith alternate motion inside said jacket and comprising a rod having acentral axis and a head, the pump also comprising an entrance devicecomprising an entrance pipe, the entrance pipe for connecting the pistonpump to a container for a fluid product, and an exit device comprisingan exit pipe for allowing exit of the fluid product from the jacket, theexit device for directing the fluid product toward a dispensing machine,said entrance and exit pipes being disposed on a first axial end of thejacket and at opposite positions radially with respect to said centralaxis, wherein the piston pump comprises a support positioned on anopposite, second axial end of the jacket from the entrance device andthe exit device, the support configured to associate said piston pumpstructurally with a dispensing machine for fluid products allowing useof the piston pump in any orientation while keeping the orientation ofthe entrance and exit pipes oriented in a common direction; wherein thepiston pump comprises a first and a second chamber each with the samecontaining volume for said fluid product, said first and second chambersbeing defined on opposite sides of said head of the piston device, eachof said chambers being connected to said entrance and exit pipes bymeans of a respective suction valve and a respective delivery valve,wherein the suction valve and the delivery valve connected to the firstchamber and the second chamber are disposed at opposite positionsradially with respect to said central axis, and the suction valve andthe delivery valve connected to the first chamber are each disposed atthe same axial position, and the suction valve and the delivery valveconnected to the second chamber are each disposed at the same axialposition, wherein during alternating motion of the piston device, astream of a fluid product sucked into the first chamber is equal inquantity with respect to a stream of the fluid product delivered by thesecond chamber and a stream of a fluid product delivered by the firstchamber is equal in quantity with respect to a stream of the fluidproduct sucked into the second chamber at a given instant in time, andwherein said entrance pipe and said exit pipe are parallel to each otherand substantially end at the same axial position near the first axialend; and wherein said entrance pipe divides into two distinct entrances,a first and a second entrance corresponding to the first and the secondchambers respectively, which allow the fluid product to enterrespectively into said first and second chambers during the suction stepin each chamber and each entrance comprises one of said suction valves,installed so as to promote flow of the fluid product into the respectivechamber, avoiding possible flows in an opposite direction; wherein saidexit pipe comprises two exits, respectively a first and a second exit,each of which comprises one of said delivery valves disposed so as toassist the flow of fluid product exiting from said two chambers; and astep motor driving said piston device in said alternate motion, saidstep motor disposed at the first axial end of said jacket with respectto the support.
 2. The piston pump as in claim 1, wherein said jacket isconfigured so as to have a bore that goes from 35 mm to 45 mm, or from50 mm to 60 mm.
 3. The piston pump as in claim 1, wherein said rod has adiameter with respect to the bore of the jacket with a ratio of nohigher than 0.25.
 4. The piston pump as in claim 1, wherein the pistondevice has a travel inside said jacket that goes from 10 mm to 15 mm. 5.The piston pump as in claim 1, wherein said head is made of PTFE.
 6. Thepiston pump as in claim 1, wherein said piston device is driven by ahigh-resolution step motor.
 7. A method for dispensing fluid productsusing a piston pump as in claim 1, comprising a first step that providessliding of the piston device from a lower end-of-travel to an upperend-of-travel, wherein the suction valve of the first chamber and thedelivery valve of the second chamber are closed and the suction valve ofthe second chamber and the delivery valve of the first chamber are open;and a second step that provides sliding of the piston device from saidupper end-of-travel to said lower end-of-travel wherein the suctionvalve of the first chamber and the delivery valve of the second chamberare open, and the suction valve of the second chamber and the deliveryvalve of the first chamber are closed, wherein the duration times of thesuction and delivery steps that occur simultaneously in said chambersare equal, and the same quantity of said fluid product passes throughsaid chambers, wherein inversion of the steps occurs at the same moment,and wherein the entrance and exit of fluid product from the piston pumpoccur on the axial end of the jacket and in directions substantiallyparallel to each other.